Which first?

[Guest]

Which do you do first, the carb sync or adjusting idle mixture?


going to follow this guide for the idle mixture http://members.dslextreme.com/users/...n_CV_Carbs.pdf


but I have read so many things over the time i have been doing this and tbh now i am not sure which one to do first

[eil]

Do the carb sync first and then adjust idle mixture, if it needs it.

[Steve]

Which do you do first, the carb sync or adjusting idle mixture?

Given the choice of just those two items, you should do the carb sync first, but keep in mind that you should check valve clearances FIRST.

The reasoning behind the 'sync first' is that you need to make sure all the carbs are working, contributing to the general operation of the engine. If, for example, one carb is virtually closed, it won't matter how much you turn the mixture adjustment screw, you won't see any change in the way the engine runs.

Following that 'throttle response' procedure is probably the best, but you can get real close if you use the vacuum gauges first. And, since they are already connected to do the carb sync, it's just one more step.

After doing the carb sync, watch the gauges and adjust the mixture screw on carb #1 (order is not really important, as long as you get them all), watching for changes in vacuum. When the engine is running at fastest idle (due to an ideal mixture), you will have a slightly higher vacuum in all cylinders. As you turn the mixture screw in a bit more, it goes away from that "happy" mixture and the engine will slow down, yielding a slightly lower vacuum. Go back to the highest vacuum level, move to the next carb. Repeat as necessary.

When you are done with that, you can verify by using the 'throttle response method'.
I have never had to re-tweak the mixtures after using the vaccum method first.

.

[Tzian]

Thanks for the explanation Steve, and yes we have done the valve clearances and put new shims in where needed

Just setting up now, keep your fingers crossed for us :P

[Tzian]

well we got the carbs balanced but just as we finished doing that her revs dropped and she conked out, she is hot now and it is late so giving up for the night before i naff off the neighbours too much, hopefully she will start up fine again in the morning when cool.

then i can try for this idle mixture setup